Here is a copy of the email I received from HAL.
If you follow the link mentioned you will get all the details.
IMPORTANT NOTIFICATION Please be advised that embarkation and disembarkation for your Rotterdam cruise departing on Sunday, August 28, will now take place in Rotterdam rather than in Amsterdam as scheduled. Cruise Terminal Rotterdam is located at Wilhelminakade 699, 3072 AP Rotterdam. Guests with Holland America Line pre-cruise hotels or transfers will be taken directly to the pier in Rotterdam. For more information regarding directions, parking information, and public transportation, please visit: https://*****/Y261EMB We look forward to welcoming you on board.